In general, a conventional switch has two states. The switch can be turned on or off manually. For normal operation, the two states are adequate to control the power supplied to an electrical appliance or electronic device. The conventional switch has a drawback that no protection is provided. As long as the switch is turned on, it stays on until it is turned off, damaged, or burned off.
In an area where electric power is not very stable, current overloading may occur frequently to a switch that controls the power supply. If the current overloading is not detected and the switch continues to operate, it is usually overheated and eventually burned out. Therefore, the current overloading problem not only results in the loss of a switch but also presents a risk of fire if it can not be detected and protected. There is a strong demand in having a switch with a protection mechanism to detect and avoid current overloading.